Functional analyses of placental protein 13/galectin-13

Nandor G. Than, Elah Pick, S. Bellyei, A. Szigeti, Ora Burger, Z. Berente, T. Janáky, A. Boronkai, Harvey Kliman, Hamutal Meiri, Hans Bohn, G. Than, B. Sümegi

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Abstract

Placental protein 13 (PP13) was cloned from human term placenta. As sequence analyses, alignments and computational modelling showed its conserved structural and functional homology to members of the galectin family, the protein was designated galectin-13. Similar to human eosinophil Charcot-Leyden crystal protein/galectin-10 but not other galectins, its weak lysophospholipase activity was confirmed by 31P-NMR. In this study, recombinant PP13/ galectin-13 was expressed and specific monoclonal antibody to PP13 was developed. Endogenous lysophospholipase activity of both the purified and also the recombinant protein was verified. Sugar binding assays revealed that N-acetyl-lactosamine, mannose and N-acetyl-glucosamine residues widely expressed in human placenta had the strongest binding affinity to both the purified and recombinant PP13/galectin-13, which also effectively agglutinated erythrocytes. The protein was found to be a homodimer of 16 kDa subunits linked together by disulphide bonds, a phenomenon differing from the noncovalent dimerization of previously known prototype galectins. Furthermore, reducing agents were shown to decrease its sugar binding activity and abolish its haemagglutination. Phosphorylation sites were computed on PP13/galectin-13, and phosphorylation of the purified protein was confirmed. Using affinity chromatography, PAGE, MALDI-TOF MS and post source decay, annexin II and beta/gamma actin were identified as proteins specifically bound to PP13/galectin-13 in placenta and fetal hepatic cells. Perinuclear staining of the syncytiotrophoblasts showed its expression in these cells, while strong labelling of the syncytiotrophoblasts' brush border membrane confirmed its galectin-like externalization to the cell surface. Knowing its colocalization and specific binding to annexin II, PP13/galectin-13 was assumed to be secreted to the outer cell surface by ectocytosis, in microvesicles containing actin and annexin II. With regard to our functional and immunomorphological results, PP13/galectin-13 may have special haemostatic and immunobiological functions at the lining of the common feto-maternal blood-spaces or developmental role in the placenta.

Original languageEnglish
Pages (from-to)1065-1078
Number of pages14
JournalEuropean Journal of Biochemistry
Volume271
Issue number6
DOIs
Publication statusPublished - Mar 2004

Fingerprint

Pregnancy Proteins
Galectins
Annexin A2
Placenta
Recombinant Proteins
Lysophospholipase
Actins
Phosphorylation
Trophoblasts
Sugars
Proteins
Affinity chromatography
Dimerization
Sequence Alignment
Glucosamine
Matrix-Assisted Laser Desorption-Ionization Mass Spectrometry
Reducing Agents
Hemagglutination
Hemostatics
Brushes

Keywords

  • Brush border membrane
  • Carbohydrate binding
  • Galectin
  • Lysophospholipase
  • Placental protein

ASJC Scopus subject areas

  • Biochemistry

Cite this

Functional analyses of placental protein 13/galectin-13. / Than, Nandor G.; Pick, Elah; Bellyei, S.; Szigeti, A.; Burger, Ora; Berente, Z.; Janáky, T.; Boronkai, A.; Kliman, Harvey; Meiri, Hamutal; Bohn, Hans; Than, G.; Sümegi, B.

In: European Journal of Biochemistry, Vol. 271, No. 6, 03.2004, p. 1065-1078.

Research output: Contribution to journalArticle

Than, Nandor G. ; Pick, Elah ; Bellyei, S. ; Szigeti, A. ; Burger, Ora ; Berente, Z. ; Janáky, T. ; Boronkai, A. ; Kliman, Harvey ; Meiri, Hamutal ; Bohn, Hans ; Than, G. ; Sümegi, B. / Functional analyses of placental protein 13/galectin-13. In: European Journal of Biochemistry. 2004 ; Vol. 271, No. 6. pp. 1065-1078.
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AU - Berente, Z.

AU - Janáky, T.

AU - Boronkai, A.

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